/* CPU control. * (C) 2001, 2002, 2003, 2004 Rusty Russell * * This code is licenced under the GPL. */#include <linux/proc_fs.h>#include <linux/smp.h>#include <linux/init.h>#include <linux/notifier.h>#include <linux/sched.h>#include <linux/unistd.h>#include <linux/cpu.h>#include <linux/module.h>#include <linux/kthread.h>#include <linux/stop_machine.h>#include <asm/semaphore.h> /* This protects CPUs going up and down... */DECLARE_MUTEX(cpucontrol); static struct notifier_block *cpu_chain; /* Need to know about CPUs going up/down? */int register_cpu_notifier(struct notifier_block *nb){	int ret; 	if ((ret = down_interruptible(&cpucontrol)) != 0)		return ret;	ret = notifier_chain_register(&cpu_chain, nb);	up(&cpucontrol);	return ret;}EXPORT_SYMBOL(register_cpu_notifier); void unregister_cpu_notifier(struct notifier_block *nb){	down(&cpucontrol);	notifier_chain_unregister(&cpu_chain, nb);	up(&cpucontrol);}EXPORT_SYMBOL(unregister_cpu_notifier); #ifdef CONFIG_HOTPLUG_CPUstatic inline void check_for_tasks(int cpu){	struct task_struct *p; 	write_lock_irq(&tasklist_lock);	for_each_process(p) {		if (task_cpu(p) == cpu &&		    (!cputime_eq(p->utime, cputime_zero) ||		     !cputime_eq(p->stime, cputime_zero)))			printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\				(state = %ld, flags = %lx) \n",				 p->comm, p->pid, cpu, p->state, p->flags);	}	write_unlock_irq(&tasklist_lock);} /* Take this CPU down. */static int take_cpu_down(void *unused){	int err; 	/* Ensure this CPU doesn't handle any more interrupts. */	err = __cpu_disable();	if (err < 0)		return err; 	/* Force idle task to run as soon as we yield: it should	   immediately notice cpu is offline and die quickly. */	sched_idle_next();	return 0;} int cpu_down(unsigned int cpu){	int err;	struct task_struct *p;	cpumask_t old_allowed, tmp; 	if ((err = lock_cpu_hotplug_interruptible()) != 0)		return err; 	if (num_online_cpus() == 1) {		err = -EBUSY;		goto out;	} 	if (!cpu_online(cpu)) {		err = -EINVAL;		goto out;	} 	err = notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,						(void *)(long)cpu);	if (err == NOTIFY_BAD) {		printk("%s: attempt to take down CPU %u failed\n",				__FUNCTION__, cpu);		err = -EINVAL;		goto out;	} 	/* Ensure that we are not runnable on dying cpu */	old_allowed = current->cpus_allowed;	tmp = CPU_MASK_ALL;	cpu_clear(cpu, tmp);	set_cpus_allowed(current, tmp); 	p = __stop_machine_run(take_cpu_down, NULL, cpu);	if (IS_ERR(p)) {		/* CPU didn't die: tell everyone.  Can't complain. */		if (notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,				(void *)(long)cpu) == NOTIFY_BAD)			BUG(); 		err = PTR_ERR(p);		goto out_allowed;	} 	if (cpu_online(cpu))		goto out_thread; 	/* Wait for it to sleep (leaving idle task). */	while (!idle_cpu(cpu))		yield(); 	/* This actually kills the CPU. */	__cpu_die(cpu); 	/* Move it here so it can run. */	kthread_bind(p, get_cpu());	put_cpu(); 	/* CPU is completely dead: tell everyone.  Too late to complain. */	if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu)	    == NOTIFY_BAD)		BUG(); 	check_for_tasks(cpu); out_thread:	err = kthread_stop(p);out_allowed:	set_cpus_allowed(current, old_allowed);out:	unlock_cpu_hotplug();	return err;}#endif /*CONFIG_HOTPLUG_CPU*/ int __devinit cpu_up(unsigned int cpu){	int ret;	void *hcpu = (void *)(long)cpu; 	if ((ret = down_interruptible(&cpucontrol)) != 0)		return ret; 	if (cpu_online(cpu) || !cpu_present(cpu)) {		ret = -EINVAL;		goto out;	}	ret = notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);	if (ret == NOTIFY_BAD) {		printk("%s: attempt to bring up CPU %u failed\n",				__FUNCTION__, cpu);		ret = -EINVAL;		goto out_notify;	} 	/* Arch-specific enabling code. */	ret = __cpu_up(cpu);	if (ret != 0)		goto out_notify;	if (!cpu_online(cpu))		BUG(); 	/* Now call notifier in preparation. */	notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu); out_notify:	if (ret != 0)		notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu);out:	up(&cpucontrol);	return ret;}